Understand the role of MHC class II molecules: They are crucial for the immune system, specifically in presenting antigens to T helper cells.
Identify the types of cells that express MHC class II molecules: These are primarily antigen-presenting cells (APCs).
List the main types of APCs: Macrophages, dendritic cells, and B cells are the primary APCs that express MHC class II molecules.
Evaluate the options given in the problem: Determine which options include cells that are known APCs.
Conclude that the correct answer is the option that includes macrophages and dendritic cells, as these are both well-known APCs that express MHC class II molecules.